Concentricity - setting up dies - runout

[dig]

Should I get out the boxining gloves? Thanks guys, been reloading for a while with accurate loads just looking to step things up a bit for a little longer range and a couple upcomming special hunts. Its one of those self debates, should I mess with what has been working for so long? Great ideas with the "o" rings and yes my dies are probably overly tight (except the forster press). You can always gleen good information from this site, or at lease get a few laughs.


Thanks,

 

[Trickymissfit]

first of all you have to have a good case from the start. A bad case will only give you bad ammo. One of the problems with everything being rigid is that you can't controll the error very much. You can have the best seater on the planet, but if the neck is not concentric you loose. Also vise versa. I think the common case holder that most presses use is a major part of the error game. The case is held in place far too rigidly, and really can't align itself with the sizer. I suppose somebody could build an attachment to allow the case body to float during the upstroke (like Forster does). No question in my mind that this would be a great stride to better ammunition. Then there is the die alignment question. Everything has some built in machining error (nature of the beast), and the O ring trick helps. I use one on the seater stem, but not on the sizer. But what I see and hear is nothing but a crutch, and never completely solves the problem. Even the highly touted Forster has a crutch, but at least makes full use of it. What we need is a better way to hold the dies in place, plus a good way to align them. The Forster lock ring is really a little too tight for me, and I have found that the Lyman rings work better for me as they allow the die to align itself a tad better. But what we really need is a ring that will align itself to the threaded body a little more accurately. I know how to do this, but it's a real pain in the butt. Also it's time to increase the die thread from .875-14 to something like 1.125-20! Better yet would be 30mm x 24tpi (standard bearing nut thread), and then use high grade Timken bearing nuts. The threads are cut very square with them, and the larger body will have much less flex with those big fat cases you guys love.

Now back to the concentricity issue. I'm about to take delivery of a NECO unit (always wanted one and the price was very good). I will now be able to do compairisons with it and my home brew unit. If readings are similar, I'll have it copyrighted. The NECO is kinda like the standard of the industry.
gary

 

[boomtube]

"Should I get out the boxining gloves? "

Nah.

 

[RDM416]

No need for the boxing gloves, Boomtube and I are just having a little fun!

I have never used the Lyman "M" type dies.

 

[sp6x6]

So I got lucky with my main rifle for LR .001-2. Just loaded it. Checked some friends and older stuff of mine some was .004-6.Wow,so start with good brass, I dont have a neck gauge, but this seems like the first big issue? So neck turn if they dont look good?Then carefull seating, sleeved seems to help?Trying to improve my loads

 

[Trickymissfit]

So I got lucky with my main rifle for LR .001-2. Just loaded it. Checked some friends and older stuff of mine some was .004-6.Wow,so start with good brass, I dont have a neck gauge, but this seems like the first big issue? So neck turn if they dont look good?Then carefull seating, sleeved seems to help?Trying to improve my loads

my NECO gauge showed up yesterday afternoon. Have not put it to the test yet, but just from looking it over, all I can say is that this is the best by a long shot! I used one a few years back (borrowed), and never knew what all it coud do. I'd rather had a .0005" indicator come with it, but even the indicator that did is a good one. Recommended!
gary

 

[boomtube]

"Have not put it to the test yet, but just from looking it over, all I can say is that this is the best by a long shot!"

Interesting appraisal.

 

[Trickymissfit]

"Have not put it to the test yet, but just from looking it over, all I can say is that this is the best by a long shot!"

Interesting appraisal.

here's what I see right away:

*will measure just about any form of case run out accurately
*will also check case wall run out
*measure loaded rounds for runout
*is capable of having more than one dial indiator in use at the same time
*will measure runout on bullets by themselves (jury's still out on this feature)
*appears to have a feature that will allow neck thickness measurement
*uses wand type indicators which are much better quality
gary

 

[TnTom]

I have found that placing a 1" square gauge block (not the rectangular style) between the shell holder and the face of the seating die as I tighten the locking ring assures the die is square to the threads and shell holder and the effect is measurable in reduced run-out. I never set up a die without taking this step.

 

[Bart B]

There's lots of misunderstanding about what causes bullet runout to be what it is. To say nothing of why different amounts of runout will be measured depending on what kind of tool's used. Especially when there's no such thing as a perfectly straight case nor a perfectly round one, either. And no tool on the market measures what most cartridge's bullet runout will be when the round fires.

Rimless bottleneck ammo's centered at the front end of the chamber when its shoulder centers perfectly in the chamber shoulder as the firing pin drives it there with great force. If the case neck's not centered on the case shoulder, even if the neck and bullet axis is parallel to the case body axis, the bullet's gonna be off center in the bore. Which is why tight chamber necks aren't any more accurate that loose ones; it's the case and chamber shoulder centers that align the front end of the cartridge; the neck free floats relative to the case.

As there's no such thing as a perfectly round chamber or shoulder, neck only sized cases will eventually grow in body diameter at the shoulder such that interference will soon be at hand. Such cases will no longer center perfectly on their shoulder 'cause the wide side of the body at the shoulder interferes with the narrow side of the chamber. Sometimes this interference causes 1 thousandths inch off-center positioning of the case shoulder to the chamber shoulder. While the firing pin's impact will help center the case shoulder in the chamber shoulder, that interference point will cause the barrel to whip/vibrate at a sllightly different direction and accuracy gets worse. Solution? Full length size all fired cases to prevent this.

Meanwhile, at the back end of the case, that's pressed against the chamber wall by the extractor pressing it there. Which means that when the round fires, the case axis is at a tiny angle to the chamber axis; front's centered at the shoulder, back's 1 or 2 thousandths off center. So every chambered round, even those with bullets and necks in perfect alignment with the case axis, are a tiny bit crooked. The amount at the bullet's tip is typically half the amount the back end of the case is off the chamber axis.

So how do we best measure bullet runout? Put the case pressure ring in a V block with the case shoulder pressed in a hole that's the diameter at mid point on the case shoulder. Now bullet runout will be measured the way it will be when the round's chambered. Any out of round at the shoulder-body junction or just the body won''t be seen. There might be a bit of out of round at the pressure ring, but that's the least important part so it doesn't matter much.

Use full length sizing dies with bushings for the neck. Expander balls usually bend necks and a bushing die usually doesn't. It doesn't matter if the sizing die axis is a bit out of line with the press ram. Shell holder flats aren't square with the die axis anyway, so what difference does it make? I know there's lots of O-rings out there wrapped around sizing and seating dies; tried several different ways of using them but the old conventional die setting ways made just as accurate ammo that shot sub 1/2 MOA 20-shot groups at 800 and 5/8ths MOA 15-shot ones at 1000.

With 30 caliber cases, runout up to 3 thousandths doesn't seem to matter. Sub 1/2 MOA at 600 yards with ammo like that's been done; with powder charges having 3/10ths grain spread inside brand new virgin cases, too.

 

[TnTom]

It doesn't matter if the sizing die axis is a bit out of line with the press ram. Shell holder flats aren't square with the die axis anyway, so what difference does it make? .

It provides the opportunity to create a square and parallel condition between the shell holder, die and ram. It can make a measurable difference so why not take advantage of the simple practice. Its because the two aren't always in good alignment that I do it and it does square it up.

I agree that the sizing button causes the biggest problem at the shoulder.

Having the resources to take more extensive measurement also helps determine where the misalignment come from. I use a Mitutoyo Coordinate Measuring Machine (CMM) that provide 3 axis measuring capability. With the ability to construct cylinders, cones, lines, planes, etc it becomes very straight forward to determine if the body,neck, and shoulder center lines as well as bullet center line are coaxial or not and if not it provides the ability to determine what the C/L relationship actually is. The fact that a cylinder can be dissected into cross section, targeting specifically the pressure ring or for that matter any cross section at any location along the case length was well as the ability to examine the relationships to the inside diameter really sheds new light on the relationships before and after firing and sizing.

I have done extensive measurement and it does make a measurable difference squaring the shell holder and die to the ram center line .

Most of the devices I have seen are very limited.

 

[Bart B]

It provides the opportunity to create a square and parallel condition between the shell holder, die and ram. It can make a measurable difference so why not take advantage of the simple practice?

When I put those O-rings under the die's lock ring, full length sized cases had a greater spread in their headspace. That's the distance from case head to shoulder datum. I think an O-ringed die's not as consistant in its vertical position as well as one conventially locked atop the press; it stays in place.

Besides, doing anything process wise in reloading that doesn't show a consistant improvement in accuracy's a waste of time for me. O-ringed sizing and seating dies haven't proved worth while for me.

 

[TnTom]

When I put those O-rings under the die's lock ring, full length sized cases had a greater spread in their headspace. That's the distance from case head to shoulder datum. I think an O-ringed die's not as consistant in its vertical position as well as one conventially locked atop the press; it stays in place.

Besides, doing anything process wise in reloading that doesn't show a consistant improvement in accuracy's a waste of time for me. O-ringed sizing and seating dies haven't proved worth while for me.

I have to tighten the die anyway so putting the gauge block in-between while doing so doesn't add any time to the process and if some variation can be minimized nothing lost.

 

[Mikecr]

Bart, what you supposedly correct with FL sizing, would be factors of fantasy, -if not for your FL sizing..
Your rationale put's a carriage before horses, and your method is self perpetuating to this rationale..

Yes, sloppy twisted ammo shoots good enough, but so does straight ammo.
At any rate, it really doesn't relate to a runout reducing endeavor.